Recently I conducted a survey on the diversity of live corals as well new coral recruits in a degraded reef to know whether the reef is self seeded or connected with other coral ecosystems. I found the diversity of new recruits were high compared to that of live corals indicating that the degraded reef is well connected with other coral ecosystem. Kindly suggest me what kind of analysis I can use to interpret this finding in a effective way.
Mani, If I were you, I would also look at satellite data or a ecomorphological atlas of coral reefs to see how close your study site is with other live sites.. this is just to prove the spatial connectivity of the reefs. This would obviate many mathematical/statistical proofs, as a satellite picture can explain the spatial connectivity in a much simpler and synoptic way.
On the other hand, if you want to prove statistically that the sample from two places (ie live corals from degraded zone and live corals from non-degraded nearby area), then a simple t-test should be enough to prove that the samples came from nearby area.. In your case t-test should statistically prove that the live corals from both the sites are similar.. hence your statement that regeneration was due to migration/influence from nearby areas is true.
Note that, I am assuming your statement - " I found the diversity of new recruits were high compared to that of live corals indicating that the degraded reef is well connected with other coral ecosystem." is true. (I am understanding your statement as - since live coral concentrations are more than some regeneration threshold, hence this new population is from another source.. I hope I am correct with this understanding).
Regards
Raghu
whether you can use a t-test depends on your data. How did you define biodiversity? Is it e.g. the number of species per area? If so, then it is probably a count and therefore the data probably follows a poisson distribution and should not be analysed with t-test I think.
I would recommend to read this paper:
A protocol for data exploration to avoid common statistical problems
by A. Zuur
http://onlinelibrary.wiley.com/doi/10.1111/j.2041-210X.2009.00001.x/abstract
You may calculate the following diversity indices and compare it through One way ANOVA. Download the PAST software from the following link.
Different diversity indices:
1. Taxa_S
2. Individuals
3. Dominance_D
4. Simpson_1-D
5. Shannon_H
6. Evenness_e^H/S
7. Brillouin
8. Menhinick
9. Margalef
10. Equitability_J
11. Fisher_alpha
12. Berger-Parker
http://nhm2.uio.no/norlex/past/download.html
Sir, With each species the breeding potential is different, so it is also important to know the adult colonies v/s its recruit ratio. In this one may require the size class also of the adult colonies. I hope the attached paper will be able to answer your question.
I agree with Stephanie. Your data would probably not be appropriate for a parametric tests (whether t-test or one way ANOVA). An option is to use permanova which has been developed for count data and is widely used in coral studies.
Ragavendra @ Dear Sir, thanks for your response. The connectivity between two different reefs is not just a matter of how close they are. Instead, the connectivity largely depends on the water current pattern existing at the time of coral spawning. I think there is a bit confusion in the way you understand my interpretation. My survey result is that, the diversity (species richness) was high among the new coral recruits compared to the adult mature coral colonies in a particular study site. Some particular coral species., for ex. Acropora formosa was present among the new recruits. Whereas the same species was absent among the adult mature coral colonies. So, obviously the larvae of that particular coral species has been supplied from some other reef where it is present.
Stefanie @ Thank you very much for the response. In this study I define biodiversity as species richness i.e. I recorded the number of different species among the new coral recruits as well the adult mature colonies in a particular study site. I found the species richness was higher among new coral recruits compared to the adult coral colonies. In addition, I have data on the density of new recruits (number of new recruits irrespective of the genera/species per m.sq). Also please see my interpretation in my reply to Ragavendra. Thanking you.
Agnes@ Thank you very much for the suggestion. Ill try analysing the results with PERMANOVA.
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